Bomb nose fuse



Nov. 20, 1945.

A. J. NICHOLAS BOMB NOSE FUSE Filed Nov. 13, 1942 2 Sheets-Sheet 1 WITNESSES:

INVENTOR Andrew 1 M'cfiqlas.

BY PM! ATTORNEY Nov. 20, 1945. A. J. NICHOLAS Boma NOSE FUSE Filed Nov. 13, 1942 2 Sheets-Sheet 2 INVENTOR Andrew J Nickolas.

ATTORNEY Patented Nov. 20, 1945 UNITED STATES PATENT OFFICE BOMB NOSE FUSE Andrew J. Nicholas, Springfield, Mass, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 13.1942, Serial No. 465,412

6 Claims.

My invention relates to aerial bomb fuses and more particularly to an improved arrangement of mechanism for arming a fuse adapted to be connected to the nose of an aerial bomb.

Aerial bombs are commonly provided with a striker rod which is adapted to be driven into a percussion device with considerable force when the bomb strikes a target. In order to prevent accidental operation of the striker rod during handling, the fuse is provided with a safety block for preventing operation of the striker rod. To render the striker rod operative, the safety block must be released during the flight of the bomb, and to this end, the fuse is provided with rotatable mechanism driven by a Wind operated propeller vane for eifecting release of the safety block.

With increasing airplane speeds trouble has been encountered in the operation of the arming mechanism, and it has been found that mechanism which operates satisfactorily at lower speeds will not operate satisfactorily at high speeds. Consequently, the number of duds due to failure of the arming mechanism has increased with higher speeds of operation in connection with the type of fuses with which this invention deals. Actual specimens taken from test bombs have shown the mechanism jammed and the gears employed to operate the arming mechanism stripped or out of effective meshing relationship.

In addition, for reliable operation of the arming mechanism, it is also desirable that the arming mechanism be capable of decreasing the time necessary to effect arming with increases in the speed of the airplane from which the bomb is released. In this respect, the arming mechanism of fuses heretofore employed has not proven entirely satisfactory.

Accordingly, one of the principal objects of this invention is to provide arming mechanism for a bomb nose fuse which will arm in shorter periods of time with increases in the speed of bomb flight, and which will provide reliable arming operation at all speeds.

A further object of this invention is to provide an improved arrangement of differential gearing for effecting arming of the bomb.

A further object of this invention is to provide an improved arrangement of differential gearing in bomb arming mechanism, in which the axial alignment of the operating gears is effectively maintained at all times to thereby prevent striping of the gears and movement of the gears out of meshing relationship.

A. further object is to provide bomb arming mechanism in which all the rotating parts are efiectively counter-balanced to prevent the effects of centrifugal force from interfering with the operation thereof.

Other objects and advantages of this invention will become apparent from the following description and accompanying drawings, in which:

Figure l is a vertical sectional view of a bomb nose fuse constructed in accordance with the principles of this invention.

Fig. 2 is a perspective view of the operating propeller and locking device shown in Fig. 1, and

Fig. 3 is a vertical sectional view similar to Fig. l of a modified form of bomb nose fuse.

Referring to the drawings, the numeral l designates as a whole a bomb nose fuse having a connecting member 2 provided with external threads by which it may be secured to the nose of a bomb in conventional manner. The connect-'- ing member 2 is provided with an internally threaded opening 3 in which a percussion device may be mounted. The opening 3 communicates with a smaller opening 4 into which the end 5 of a striker rod 6 projects. The striker rod 6 is pro-- vided with a head 1 and aspring 8 for maintaining the head 1 and rod 6 in position shown in Fig. 1. To prevent accidental operation of the striker rod 6, a safety block 9 is provided intermediate the head I and body of the fuse l and the striker rod 8 is rendered operative after release of the safety block 9 in a manner to be described. The striker rod 6 is driven into a percussion cap, not shown, mounted in the opening 3 with considerable force when movement of the head I is arrested by striking an object after the bomb is released from an airplane.

The safety block 9 is provided with an arming sleeve I0 controlling its operation. The function of the arming sleeve I0 and the construction and operation of the safety block 9 are well known in the art, and it will be understood that this invention is limited to the mechanism for effecting reliable operation of the arming sleeve It]. With respect to the safety block 9 and arming sleeve it, it is sufficient to point out that the safety block 9 is rotated during the flight of the bomb and is removed by centrifugal force after the sleeve It has been moved downwardly, as shown in the drawings, to an arming position where it will not interfere with the outward movement of the safety block 9. The safety block 9 is in the nature of a cylindrical member having an opening II at one side thereof sufiicient to clear the spring 8 and striker rod 6. The opening II on balances the member 9,- thereby causing a centrifugal force upon rotation thereof which will be effective upon movement of the sleeve It] to a position beneath the lower surface l2 of the block 9 for moving the opening I 1 toward the striker rod 6 and thence outwardly from underneath the striker head 1.

The arming sleeve 10 is internally threaded at its lower end and has threaded engagement as at 13 withexternal threads formed'on a stationary arming hub l4 projecting upwardly from a base member [5 which is secured to the member 2 by a housing 16. Upon rotation of the arming sleeve [0 with respect to the arming hub 14; the sleeve l0 will be moved downwardly to its arming-posi' tion for efiecting release of the safety block 9. Rotation of the arming sleeve H] with respect to the hub I4 and housing i6 is effected by differential gearing comprising a gear I! secured to the arming sleeve Ill, a gear [8 secured to the arm- 5 ing hub l4, and a pinion l9 meshing with both the gears l7 and I8. mounted on a shaft having its lower end anchoredin an'annular member 2 I and its upper end anchored in an annular member- 22.- Theannular member 2| is provided with an annular notch as at 23 for the receptionof ball bearings 24 to thereby provide a ball bearing race for the member 21' about the stationary part I5. The housing l6is provided with an annular notch as at 25 1 for the reception of ball-bearings 26 tothereby provide a ball bearing race fortheannular member 22 within'the housing 16. Rotation of the members 2| and 22 is effected by-means of apropeller 21 secured to a block 28' having a threaded connection to theupper endof the annular member .22-. Uponrotation of the propeller 21, the parts-20',-2 I- and 2-2 will be rotated as a unit about the gears I1 and I8 to effect arming operation of the sleeve --l0.- As best" shown in Fig. 2, the

propeller 21-is provided with vanes 29 effective upon movement ofthe bomb through the air after its release'to rotate the propeller 27.

The-{gears H andlfljhave the same pitch diameter butar'eprovided with adifferent num 'berof-teeth in order that rotation of the gears I1 and sleeve lawith respect to the stationary parts maybe effected; In an-actua'lmodel, the arming hubgear I8 is provided "with 35 teeth "and the arming sleeve gear 17" is provided with 36 teeth,-and the' pinion I9'is provided with 12 teeth.

Accordingly, it will be apparent that the gear i! willbe rotated"through the pitch of one tooth upon one 'complete revolution of the shaft 20 about the gear l8,'*and that during this time the pinion iawillrotate' 3.9l're'volutions about its shaft '20. :55,

It will thus be seen that a'c'omplete revolution ofthe 'gearl'! with respect to the gear I8 will'be had'fafter "36"revoluti0ns of theshaft 20 about the'gearl8.' Since the threads I3 are formed at 32 threads per'inch in the actual model referred to, it will be 'sen'that 'a complete revolution of The pinion I9 is rotatably the"gear"l1 will"move the arming sleeve down wardly of an inch toward its arming' 'position.

The number of revolutions which the gear l 'l must make is," therefore; dependent upontthe length of the 'sleevep'orti'on" [0' extending upwardly within 7 the safety block a.

The difficulty of 'securingefiective operation i will be more readily appreciated when it is considered that complete movement of the sleeve Into arming position must be had in a few seconds at the lowest speed of operation and in decreasing periods of time at higherspeeds of operation; w The problems encountered will be ut-F ier. appreciated W nit is con a the scale of the drawing of Fig. 1 is approximately 3 times as large as the size of the actual fuse. V

At the speeds of operation necessary, a small amount of friction or slight misalignment of the moving parts of the operating mechanism will be effective to interfere with the operation thereof. The arming mechanism of this invention is efiective to maintain the rotating parts thereof in axial alignment concentrically of the housing It and to prevent direct frictional engagement between the relatively movingsurfaces of the housing l6 and rotating parts.

This is accomplished by reason of the fact that the rotating parts comprising the members 2| and 22 and the parts connected thereto constitute a unit, the position of which is eifectively maintained within the housing I6 by the lower bearings or race 24, and the upper bearings or race 26. It will be apparent that'these bearings being spaced from each other along the housing I6 are effective to align the position of the rotating unit and to absorb the thrust of such unit on the h'ousing" l6. Any

serious frictional engagement of surfaces on 'therotating unit with relatively stationary surfaces on the housing It is thus effectively prevented.

The support for the pinions I9 providedby the annular members 2! and 22 effectively anchors both ends of the pinions [9, since the shafts 2n have their ends respectively anchored in the members 2| and 22. This arrangement effectively prevents misalignment of the axes of the pinions l9 during assembly of the fuse, which misalignment would otherwise be possible in view of the delicacy-and lightness of the pinion supporting shaft. 1 I I The mounting for the pinion I9 provided by the members 2! and 22, in effect, provides a gear cage which is-rotatable about the gears I1 and 18.

In this arrangement it will be noted that the gear 49 is a planetary gear-which rotates about the axis of'the shaft 20 and also about the sungears I1 and I8.

In order to balance out the efiect of centrifugal force due to the rapid rotation of the pinion l9 about the axis of the gears l1 and It, a counterweight l9a is mounted in position at a point diametrically opposite the pinion l9. In this manings M and 32, undesirable operation of the arming mechanism may be prevented prior to the release of a bomb from an airplane, In order to'positively drive or rotate the safety block 9,

the propeller 2'! is provided with an up-turnedin a -slot 35 formed portion 34 for engagement in the safety block 9.

In'the intended operation-of the bombfuse, the-propelIerZ'L is rotated so as to move thearming sleeve downwardlyt However, it is possiblefor thersleeve H] to move upwardly due to" reversal of rotation of 'the propeller for some reason such as, for example, turning over of the bomb. after it is released from the airplane;- Such reversal of rotation and upward movementof w x axis of the the arming sleeve l might interrupt the threaded connection I3 between the arming sleev Iii and arming hub id. To permit such interruption of the threaded connection I3 without damage a coil spring 36 is provided. The coil spring is deformed in such manner that a portion thereof will rest on the upper surface of the gear ll, as viewed in Fig. 1, and another portion thereof will engage with an annular ledge 31 on the innor surface of the annular member 22. Upon reversal of rotation tending to move the sleeve HI upwardly from the position shown in Fig. 1, the deformed spring 36 will be compressed prior to interruption of the threaded connection 13. Such compression of the spring 36 will provide a bias tending to move the arming sleeve In toward the arming hub l4 so as to automatically reestablish the threaded connection l3 upon sub sequent rotation of the parts in their normal intended manner. The spring 36 and its relation to the parts described above provides a device in the nature of an overrunning clutch which permits free rotation of the sleeve II] in a reverse direction without damage and is operative to immediately reestablish the connection upon rotation in an opposite direction. Were it not for the spring 36 and the construction enabling disengagement of the threaded connection 13, continued upward movement of the sleeve H] would be had until the gear I'l engaged with the annular member 22. Thereafter the differential gearing would operate as a jack and either press the gear I! oif th sleeve [0 or so deform it as to render the same useless.

The modification illustrated in Fig. 3 is essentially the same as that shown in Fig. 1, except for the parts to be described, and lik numerals have been employed to designate like parts. The essential difference of the construction illustrated in Fig. 3 lies in the arrangement of gearing for operating the sleeve H). In this showing, it will be noted that the arming sleeve ID has a threaded connection 13 to an arming hub 60 which is rotatable instead of stationary as is the case with the arming hub 14 of Fig. l, the arming hub 40 being connected directly to the propeller 27 for rotation thereby. The arming hub 40 is provided with an internal gear 4i and the arming sleeve of Fig. 3 is provided with an internal gear. 42, the internal gears 4i and 42 being difierentially related and meshing with a pinion 43 rotatably mounted on a stud M projecting upwardly from the base l5. The stud 44 is provided with an opening through which the striker rod 6 may project into the opening 4 for movement into the chamber 3. The advantage of this arrangement of gearing lies in the fact that a larger pinion 43 may be obtained thereby enabling a larger number of teeth to engage with the gears 4| and 42, thus reducing the stress on the gear teeth. In this construction, the striker rod 6 is offset from the center of the housing It and an additional striker rod 45 may be employed and driven into an annular chamber 46 adapted to contain a capsule for providing a time delayed explosion of the bomb. The modification of Fig. 3 operates in the same manner as that of Fig. l, and it will be noted that the bearings 24 and 26 function to maintain the alignment of th rotating parts and absorb end thrust on the housing IS in the same manner as in Fig. 1. A spring 36 is engaged with the arming sleeve ill and functions in the same manner as does the spring 36 in Fig. 1. The safety block 9 is of a different type from that shown in Fig. 1, but is a type well known in the art and need not therefore be referred to in detail.

From the foregoing, it will be apparent that there is provided an arming mechanism for bomb fuses having a differential gear unit for operating the same in which the rotating parts are effectively maintained aligned, and in which sliding frictional engagement of relatively moving surfaces is effectively eliminated. By maintaining the position of the rotating parts aligned, the stability of the structure in operation is increased and such structure will function reliably at increased speeds of operation to arm the fuse in decreasing periods of time.

Since certain changes may be made in the above construction and difierent embodiments of the-invention may be made without departing from thescope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a fuse housing the combination of a housing for connection to the nose of an aerial bomb, the combination of a sleeve movable axially with respect to said housing to an arming position, and driving means for said sleeve comprising an arming hub having a threaded connection with said sleeve, a pair of difierential gears respectively mounted on said hub and said sleeve, a planetary gear engaged with said differential gears, a cage for said planetary gear comprising a pair of parts rotatably mounted in said housing, each of said parts respectively supporting an end of said planetary gear, and a propeller connected to one of said parts for rotating said cage and thus rotating the planetary gear about said dilferential gears.

2. The combination claimed in claim 1 wherein said planetary gear is provided with a counterbalance mounted on said gear cage.

3. The combination claimed in claim 1 wherein said arming sleeve is moved to arming position upon rotation of said cage in one direction, and said sleeve and hub are disengaged upon rotation of said cage in an opposite direction, together with resilient means compressible upon disengagement of said hub and sleeve and. eifective to provide a biasing force to reengage the threaded connection between said hub and sleeve upon subsequent rotation of said cage in said one direction.

4. In a fuse having a housing for connection to the nose of an aerial bomb, the combination of a sleeve movable axially with respect to said housing to an arming position, and driving means for said sleeve comprising an arming hub having a threaded connection with said sleeve, and means for rotating said sleeve, said sleeve being movable to arming position upon rotation in one direction, and out of threaded engagement with said hub upon rotation in an opposite direction, and resilient means compressible for exerting a bias to maintain said sleeve in a position reestablishing said threaded engagement upon subsequent rotation of said sleeve in said one position.

5. In a fuse having a housing for connection to the nose of an aerial bomb, the combination of a sleeve movable axially with respect to said housing to an arming position, and driving means for said sleeve comprising an arming hub having a threaded connection with said sleeve, 9. pair of diiferential gears respectively mounted on said hub and said sleeve, a planetary gear engaged with said diiferential gears, a cage for said plan-' etary gear comprising a pair of parts rotatably mounted in, said housing, each of said parts respectively supporting an end of said planetary gear, a ball bearing race positioned between each of said partsrand said housing, said races being effectivepto position said cage concentrically of said housing and to absorb the end thrust of said cage in said housing, and a propeller connected to one of said parts for rotating said cage and thus rotating the planetary gear about said differential gears.

6. In a fuse having a housing for connection to the nose of an .aerial bomb, the combination of, a sleeve movable axially with respect to said housing tov an arming position, driving means forsaid sleeve comprising a sleeve-like arming hub having a threaded connection with said sleeve, two internal gears mounted-respectively,

on said hub and on said sleeve, said gears having different numbers of teeth, a pinion carried by said housing meshingwith each of said gears ing movable to arming position upon rotation of said hub in one direction and, upon rotation ofsaid hub in the opposite direction, said sleeve and V hub are moved out of threaded engagement, and

resilient means compressible upon disengagement of the threaded connection of said sleeve and hub.

and effective to provide a biasing forcetto re-' establish said threaded connection between said hub and sleeve upon subsequent rotation of said sleeve in said one direction. 1

ANDREW J. NICHOLAS. 1 

